The invention relates to soluble organic-inorganic compositions comprising linear and cyclic carbosiloxane components, to a novel process for preparing them and to their use as coating materials.
Polyfunctional cyclic carbosiloxanes have already been described. By way of example, U.S. Pat. No. 6,005,131 and WO-A 94/96807 disclose monomeric polyfunctional cyclic carbosiloxanes from which, in combination with metal alkoxides, organic-inorganic hybrid materials can be produced with the aid of the sol-gel process. These materials can be used, for example, for coating surfaces. The coatings thus obtained are distinguished by good solvent resistance and chemical resistance and also by a high level of mechanical wear resistance.
Various processes for preparing polyfunctional cyclic carbosiloxanes are disclosed in U.S. Pat. No. 4,461,867, 4,525,400 or 6,136,939. A disadvantage of the prior art processes cited is that for preparing polyfunctional carbosiloxanes they use pure cyclic hydrosiloxanes or pure cyclic alkenylsiloxanes as precursors. The preparation of cyclic hydro- and alkenylsiloxanes with a high level of purity is described, for example, in EP-A 0 967 236, U.S. Pat. No. 5,189,193, DE-A 1195752 and DE-A 4414690. In order to achieve the level of purity in the precursors that is required for the synthesis of cyclic carbosiloxanes, however, complex and thus costly work-up methods are needed.
A further disadvantage of the preparation processes known to date is their complex technical implementation, which has so far stood in the way of an industrial realization of these processes.
For preparing monomeric polyfunctional carbosiloxanes, WO-A 94/06807 and U.S. Pat. No. 4,525,400 disclose, for example, processes in which alkenylalkoxysilanes are reacted with organohydrocyclosiloxane by means of a hydrosilylation reaction. So that reaction is quantitative the alkenylalkoxysilane is used in excess. When reaction has ended unreacted precursor is removed by distillation. In U.S. Pat. No. 4,525,400 the reaction takes place in a solution with a concentration of 20% by weight, leading to a low space/time yield.
A disadvantage of the prior art processes described is that it is not possible to prepare organic-solvent-soluble condensation products of polyfunctional carbosiloxanes.
Further processes for preparing monomeric polyfunctional cyclic alkoxy- and hydroxy-functional carbosiloxanes are described in U.S. Pat. Nos. 6,005,131 and 5,880,305. The first reaction step comprises addition of a hydrochlorosilane to an alkenylcyclosiloxane. This is followed by hydrolysis or alcoholysis to give the corresponding monomeric polyfunctional cyclic carbosiloxanes. Since as a result of the required activation energy the hydrosilylation must be carried out preferably at elevated temperatures, there exists with this process the problem that, owing to the low boiling points of the hydroalkylchlorosilanes, fractions of the hydroalkylchlorosilane may escape from the reaction vessel during the reaction. A consequence of this is that unreacted alkenyl groups can remain in the end product and may adversely affect the quality of the product. With these processes, therefore, the degree of reaction after the hydrosilylation must be monitored by analysis and, where appropriate, further hydroalkylchlorosilane added. It is also possible directly to use an excess of hydroalkylchlorosilane, but such an excess must be removed again by distillation following the reaction.
A process for preparing soluble oligomeric cyclic alkoxy- or hydroxy-functional carbosiloxanes is described in U.S. Pat. No. 6,136,939. With this process as well, however, the above-described disadvantages occur.
An object of the present invention was therefore to provide compositions of polyfunctional carbosiloxanes which are soluble in organic solvents, a novel process for their preparation, and their use.